1. Field of the Invention
The present invention relates to a solid electrolytic capacitor and a method of manufacturing a solid electrolytic capacitor.
2. Description of the Related Art
A solid electrolytic capacitor having a conductive polymer layer as an electrolyte has conventionally widely been known as a capacitor suitable for reduction in size. In order to achieve a further greater capacity in such a solid electrolytic capacitor, a technique to increase a surface area of an anode element by etching a surface of an anode element made of a metal foil or employing a metal sintered body as an anode element has been adopted.
For example, Japanese Patent Laying-Open No. 7-122464 discloses manufacturing of a solid electrolytic capacitor by forming a dielectric film composed of tantalum oxide on a surface of a sintered body by anodizing the surface of the sintered body of tantalum and by forming a conductive polymer layer on the dielectric film. In addition, this publication discloses completely covering the inside of fine holes formed in the surface of the sintered body with the conductive polymer layer.
As a result of the studies made by the present inventors, however, it has been found that it is difficult to completely cover the inside of the fine holes in the anode element with the conductive polymer layer and a part of the dielectric film is exposed without being covered with the conductive polymer layer. If such a solid electrolytic capacitor is placed, for example, in an environment at high humidity, external moisture permeates and diffuses in the solid electrolytic capacitor and directly comes in contact with the dielectric film, resulting in increase in capacity of the solid electrolytic capacitor. A solid electrolytic capacitor of which capacity varies depending on an environment is low in reliability.